TL;DR - went hard ass on my dog and it is fixing her bullshit games on retrieve.

My 3yo GWP the last 2 years has done great on birds.  She finds birds, hunts dead, and points/backs points as well as any dog.  My one big frustration was on retrieve she would do about 87 victory laps and some avoidance behavior because she didn't want to give up the bird/dummy/ball/stick.  She isn't hard mouthed, she just likes carrying the object around.  It takes 2 hands to get the object away from her.  You have to catch her collar with one hand and the other has to pry the object out of her mouth.  This means I have to lay my shotgun on the ground on each bird.  Super annoying.

This spring I started watching "Smart Fetch" videos and realized that I had done most of that already and that the dog knows what she is supposed to do, I was just letting her get away with not doing what she was supposed to do.  I put on her e-collar a couple of nights ago and we went to the park to play fetch.  It took two nicks (level 3 out of 16) to get her to realize I meant business it was all retrieve straight to hand after that.  A couple of times she dropped the ball at my feet, I made her pick up the ball and deliver to hand before she was praised and I threw it again.  All of it is a 1 handed operation.

I was hesitant to use the collar before because I didn't want to put her off retrieving

We still need to get to a reliable conditioned retrieve without the threat of the collar and conditioned release and hold commands, but this is a major improvement.  Repetition will finish the job.

The e-collar is my favorite tool.

I would slowly eliminate the threat of shock, or transition it. I mean make sure the shock goes the same time as the beeper, then once she figures that out just use the beeper but whistle at the same time. She will obey the chain as long as they lead back to that chance of getting zapped.

I found with my hound that a quick tune up about once a year or less would help him remember his manners.

Yep - I've used the e-collar since she was a pup, but I was always afraid to nail her while carrying a bird.  I shouldn't have been.

I only had to pop her the first 2 times out, now she is being perfect.  I'm leaving the collar on for now, will for several weeks.  

Beep on the collar with her is a combination of recall and check in.  One beep she comes back close enough to see what I want, then if I want her to work a piece of cover I think she missed or go another direction I can point her at it.  Two beeps is "come".  Works pretty well in the field, no whistling or yelling.

Out hunting she always wears the collar, especially for the GPS functionality.  We hunt in really tall cover, usually the only way to see where she is is watching the grass move.  When she stops and points, frequently I have no idea where she is or even what direction without the GPS.